the only way this happens is three ways
1: Fireteam literally saw where you went and you stood still so they just spotted you
2: Fireteam heard your clicking or you prepping a ranged weapon did lil spray and then spotted you (you can hear the plasma canon charging and the bow charging)
3: they see some environment detail that gives you away (branch movement plant sway) AI literally aiming at the predator sometimes (like the snipers who have Red DOTS that you can track like the caster lazer)
any other situation your encountering cheaters cause unless you stood on a camp rooftop for literally minutes there is not a situation where this happens and it’s not your fault